1. Field of the Invention
The present invention relates to an air filtration unit for a clean room, more particularly, to an air filtration unit for a laminar flow clean room, which includes an isolation bar inserted into a filtering member thereof at a position corresponding to a partition panel installed in the clean room, so as to permit easy and rapid change in the layout of the clean room when moving or installing partition panels. The use of the isolation bars permits panels to be installed in positions crossing filtering members, while preventing turbulence downstream of the areas where the panels would otherwise block air flow through the filtering members.
2. Background of the Related Art
With increasingly precise manufacturing requirements, many industries are now demanding far greater purity and cleanliness standards to ensure high product efficiency and high production yields.
In particular, in the semiconductor, pharmaceutical, genetic engineering and material development fields, even a small number of microscopic contaminants such as dust particles contained in the air may cause poor quality products or failure to meet critical test parameters. Accordingly, contaminant control of the air is an important and growing concern, and as such, developments are continuing in an effort to achieve clean room systems that are capable of tightly controlling the contaminants in the air.
A clean room system typically comprises air supply and air exhaust areas that are in flow communication with a clean area. In the clean area, various pieces of equipment for fabricating or testing predetermined products are disposed. Air is supplied from the air supply area into the clean area through the ceiling of the clean area. The air in the clean area is then exhausted through the floor of the clean area and into the air exhaust area. Thereafter, the air supply area intakes air from the air exhaust area and supplies the air into the clean area. In such a manner, air is re-circulated in the clean room system.
The re-circulated exhaust air is filtered by air filtration units that are mounted on the ceiling of the clean area prior to flowing into the clean area. Each of the air filtration units is connected to a fan. The air filtration unit also includes a filter, which is generally 1200 mm.times.600 mm in size. The cleanliness level of the clean area depends on the performance of the filters.
In semiconductor fabrication, high efficiency particulate air (HEPA) filters or ultra low penetration air (ULPA) filters have been used for filtering the air. HEPA filters can filter over 99.97 percent of particles of 0.3 .mu.m or larger. ULPA filters can filter over 99.99 percent of particles of 0.12 .mu.m or larger.
The clean area is divided into three sub-areas: a work area in which operators work; a process area in which semiconductor fabricating equipment is disposed; and a service area in which the fabricating equipment is disassembled and checked. Panels having a predetermined thickness are used to partition the clean area into the sub-areas. The panels are fixedly and perpendicularly mounted along connections between the air filtration units.
However, when the layout of the clean room needs to be changed due to rearrangement of the fabricating equipment, or due to upgrades of the fabricating equipment, the panels must be rearranged and mounted according to a new layout. In some cases, the panels may have to be mounted across the center of a filter, rather than along the connection between the air filtration units as described above. However, when a panel is mounted across the center of a filter, the panel acts as an obstruction that disrupts the smooth downstream air flow. In addition, particles may be generated due to turbulence occurring at the boundary portion where the panel crosses the filter.
To overcome such disadvantages, half-sized filters, i.e., filters of 600 mm.times.600 mm in size, have been provided. Thus, two 600 mm.times.600 mm filters are used instead of one 1200 mm.times.600 mm filter. When the 600 mm.times.600 mm filters are used, the panels are not mounted across the center of the filters. However, the 600 mm.times.600 mm filters have disadvantages in that additional work is required for installation, and costs are increased because the smaller filters require additional mold bars for holding and supporting them.
Furthermore, each of the 600 mm.times.600 mm filters requires a separate fan in order to prevent turbulence from being generated at the gap between the mold bars holding and supporting the filters. As a result, compared with the 1200 mm.times.600 mm filters, the 600 mm.times.600 mm filters need twice as many fans, thereby increasing both costs and power consumption.